heres some help:
ipod touch has
5 hours battery life for video playback (includes web browsing, game playing, and naything else with the screen)
22 hours battery life for music playback.
so if your ipod is just barely in the red youve still got almost an hour of games left and a couple hours of music left.

There's far too many variables on the touch that make anything near an accurate battery life time remaining useless. It would never be close. I mean, use the music player, and the Safari, and have a couple of apps open. Soon enough, your battery icon in the top corner will look very low. Maybe 25% remaining. BUt if you close some aps and put the iPod to sleep. when you come back, you may notice that you have overhalf your battery remaining.